This invention relates generally to gas turbine engine rotors and, more particularly, to fuel system interfaces used to prevent rotor over-speeds.
Gas turbine engines typically include over-speed protection systems that provide rotor over-speed protection. Typically the over-speed protection systems either hold rotor speed below critical rotor speeds or shut off fuel flow with an electronic signal. One type of known protection system receives over-speed signals from mechanical speed sensors. The mechanical speed sensors include rotating flyweight sensing systems that indicate an over-speed condition as a result of the rotor rotating above the normal operational maximum speeds, yet below the structural failure limits. The flyweight sensing systems are hydraulically coupled to a bypass valve, such that as the flyweights are forced centrifugally outward, the bypass valve is operated to reduce a differential pressure across a fuel metering valve at a fixed value. Thus, fuel flow to the engine is controlled by the flow area of the metering valve.
Other types of known over-speed protection systems receive over-speed signal information from electronic control sensors. Additional mechanical control sensors derive over-speed conditions as a function of an engine fuel flow pressure. Such systems provide for rapid fuel shutoff and resulting engine shutdown if engine speed exceeds the normal maximum value.
Because the protection systems are non-redundant, over-speed protection system architecture varies depending on whether the protection system receives a signal from an electrically or mechanically controlled system. Because of the various system architectures, an elapsed time for the protection system to react to an over-speed condition may vary depending on the type of sensing system used to detect the over-speed condition and a location of the sensing system sensors relative to the protection system.